In cardiomyopathy, the heart muscle becomes enlarged or abnormally thick or rigid. In rare cases, the muscle tissue in the heart is replaced with scar tissue.
As cardiomyopathy progresses, the heart becomes weaker and less able to pump blood through the body. This can lead to heart failure, arrhythmias, fluid buildup in the lungs or legs, and, more rarely, endocarditis (a bacterial infection of the lining of the heart). The weakening of the heart also can lead to other severe complications. The four main types of cardiomyopathy are:
Dilated cardiomyopathy - the most common form of cardiomyopathy. It generally occurs in adults aged 20 to 60 years. Men are more likely than women to develop dilated cardiomyopathy. Dilated cardiomyopathy affects the heart's ventricles and atria - usually starting in the left ventricle, where the heart muscle begins to dilate or stretch and become thinner. This leads to enlargement of the inside of the ventricle. The problem often spreads to the right ventricle and then to the atria as the disease gets worse. When the chambers dilate, the heart can't pump blood very well. The heart tries to cope by dilating the chambers even more. Over time, the heart becomes weaker and heart failure can occur. Dilated cardiomyopathy also can lead to heart valve problems, arrhythmias, and blood clots in the heart. Having advanced dilated cardiomyopathy is a common reason for needing a heart transplant. Up to one-half of all cases of dilated cardiomyopathy may be hereditary (passed down in the genes from parent to child). These cases are called familial dilated cardiomyopathy. Dilated cardiomyopathy also can be a complication of many conditions, including coronary artery disease and high blood pressure. It also can be caused by viral infections, excessive use of alcohol, and exposure to certain drugs (including cocaine, amphetamines, and some drugs used in cancer treatments).
Hypertrophic cardiomyopathy - occurs when the heart muscle thickens abnormally, generally in the left ventricle, and is classified as either obstructive or nonobstructive. In the obstructive type, the septum (the wall that divides the left and right sides of the heart) thickens and bulges into the left ventricle. This bulge blocks the flow of blood out of the ventricle. The ventricle must work much harder to pump blood past the blockage and out to the body. Obstructive can also affect the heart's mitral valve, causing blood to leak backward through the valve. In the nonobstructive type, the thickened heart muscle does not block the flow of blood out of the ventricle. The entire ventricle may become thicker or it may happen only at the bottom of the heart. The right ventricle also may be affected. In both types, the thickened muscle makes the inside of the left ventricle smaller so that it holds less blood. The walls of the ventricles also may become stiff. As a result, they are less able to relax and fill with blood. Changes also occur to the cells in the damaged heart muscle. This may interfere with the heart's electrical signals, leading to arrhythmias. Some people with hypertrophic cardiomyopathy have no symptoms, and the condition does not affect their lives. Others have severe symptoms or develop complications such as serious arrhythmias. A few people with the condition have sudden cardiac arrest because of dangerous arrhythmias. It can be inherited because of a gene mutation or develop over time because of high blood pressure or aging. Often, the cause is unknown.
Restrictive cardiomyopathy - tends to mostly affect older adults. In this type, the ventricles become stiff and rigid due to replacement of the normal heart muscle with abnormal tissue, such as scar tissue. As a result, the ventricles cannot relax normally and expand to fill with blood, which causes the atria to become enlarged. Eventually, blood flow in the heart is reduced, and complications such as heart failure or arrhythmias occur. It can occur for no known reason, or it can develop because the person has another disease. Some of the diseases that can cause restrictive cardiomyopathy include hemochromatosis, sarcoidosis, amyloidosis, and connective tissue disorders. Restrictive cardiomyopathy also can occur as a result of radiation treatments, infections, or scarring after surgery.
Arrhythmogenic right ventricular dysplasia (ARVD) - a rare type of cardiomyopathy that develops when the muscle tissue in the right ventricle dies and is replaced with scar tissue. This process causes problems in the heart's electrical signaling, resulting in arrhythmias. ARVD usually develops in teens or young adults and is often the cause of sudden cardiac death in young athletes. ARVD is thought to be an inherited disease.
Signs & Symptoms
Some people with cardiomyopathy never have symptoms, and others have no symptoms in the early stages of the disease. As cardiomyopathy progresses and the heart weakens, signs and symptoms of heart failure usually appear. These signs and symptoms include:
Shortness of breath after exercise or even at rest
Swelling of the abdomen, legs, ankles, and feet
Other signs and symptoms can include dizziness, lightheadedness, fainting during exercise, abnormal heart rhythms (arrhythmias), and an extra or unusual sound heard during the heartbeat (heart murmur).
Cardiomyopathy is diagnosed using a medical history, physical exam, and tests such as chest x ray, electrocardiogram, echocardiogram, stress test, and blood tests. Because cardiomyopathy often runs in families, doctors may recommend that the parents, brothers and sisters, and children of people with cardiomyopathy be tested for the disease. Treatments depend on the type of cardiomyopathy, how severe the symptoms and complications are, and the age and overall health of the person. The main goals of treatment are to manage any conditions that cause or contribute to the cardiomyopathy, control symptoms, stop the disease from getting worse, and reduce complications and the chance of sudden cardiac death. Treatment may involve medicines, surgery, nonsurgical procedures, or lifestyle changes.